The invention relates generally to processing between two fluid streams of different compositions, and particularly to a hybrid multichannel structure having a porous body with channels for separation, purification, mass transport, exchange, or other types of processing applications of process streams.
For water filtration, existing monolith structures use a cross-flow filtration configuration in which a single feed stream that enters the filtration channels of a ceramic membrane element is divided into a permeate (solution that passes through the membrane and exits transverse to the monolith flow path) and a retentate (solution that is retained by the membrane and exits parallel to the monolith flow path and is recycled back into the feed stream). Such a monolith structure 100 is shown in FIG. 5 and includes a housing 102 having a plurality of ceramic membrane monoliths 104 disposed therein. The housing 102 is typically made of 316L Stainless Steel that incorporates a standard 150# raised-face bolt flange for connecting to a standard 150# RF counter-flange. The permeate ports are standard threaded pipe connections. The ceramic membrane monoliths 104 are sealed in the housing 102 using polymeric gaskets with a choice of materials to fit specific needs.
Referring now to FIGS. 6 and 7, each monolith 104 includes a ceramic support 106 of alpha-alumina having multiple filtration channels 108 incorporated in monolithic support material. The channels 108 can vary in diameter and can be present in multiple numbers, such as the nineteen channel membrane depicted in FIG. 6. A membrane layer 110 of metal oxide coating is formed on the inside of axially oriented channels 108. The ceramic membrane monolith 104 including the ceramic support 106 with the membrane layer 110 depicted in FIG. 6 is commercially available from Pall Corporation of Deland, Fla. under the tradename MEMBRALOX®. A standard range of MEMBRALOX® membrane layers and their composition are as follows:
Microfiltration: 0.1-12 microns (μm) (Alpha Alumina)
Ultrafiltration: 20-100 nanometers (nm) (Zirconia)
Nanofiltration: 1000-5000 daltons (D) (Titania)
As a feed stream 112, such as water 114 containing particles 116, flows into the channels 108 lined with the membrane layer 110, the permeate 118 passes through the pores of the membrane layer 110 and underlying support 106 in a cross-flow or tangential flow. The retentate 120 is essentially the original feed stream 112, but now contains a higher concentration of large molecules and/or particles retained by the membrane layer 110, as shown in FIG. 7. The separation is driven by the pressure difference from one side of the membrane to the other, commonly referred to as transmembrane pressure.
The parallel flow of the feed stream, combined with the boundary layer turbulence created by the cross-flow velocity, continually sweeps away particles and other substances that would otherwise build up on the membrane surface. As a result, cross-flow filters inherently maintain high permeation rates longer than conventional dead-end filters.
As described above, the monolith structure 100 for liquid separation includes a single feed stream 112 and two output streams (the permeate 118 and the retentate 120). However, for high-temperature gas separation, it is often advantageous to use two discrete feed streams in which one of the feed streams is a sweep to keep permeate concentration low to maximize the driving force for separation. This requires two discrete flow paths in fluid communication only through the porous walls of the monolith structure. Thus, there is the need for a hybrid structure for high temperature gas separation, such as for hydrogen gas separation.